ASI color balance

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deanST
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ASI color balance

Post by deanST »

I am about to embark on using filters on some nebula targets of interest with
either my Optolong L-eNhance or IDAS LPS-D3 and thought this might be the best time
to re-configure how I capture data in KStars/Ekos. The main guiding principle in StarTools
is to execute best practices as much as possible in data capture and so I am thinking
that the 2 white balance factors from red and blue should be set to neutral/off at 50 and 50.
What difference will this make upstream in calibration, registration
and stacking, in Siril or ASTAP, and downstream in StarTools for final processing ?
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Re: ASI color balance

Post by admin »

Hi,

I am assuming you are using an OSC or DSLR?

Ideally, you would not have any white balancing done during capture, so if 50/50 means "off" in your software, definitely use that.

When you open up your OSC or DSLR dataset in StarTools with the first option and then do an AutoDev, you will probably see a cyan-ish bias (typical when acquiring with an LP or duoband filter). If so, you are on the right track. If not, something may be not quite right. Here to help if this happens.

If using an OSC/DSLR, import your dataset via the Compose module, loading the dataset three times; once for red, once for green, once for blue.
Set "Luminance, Color" to "L + Synthetic L From R(2xG)B, R(GB)(GB) (Bi-Color from OSC/DSLR)".
If all is well and the dataset originates from an OSC or DSLR, and was not color balanced, then this will let you process your daset with the highest luminance fidelity.

Once you hit the Color module, start of with the Bi-Color preset, and choose a Matrix option you like for your bi-color rendering. When color balancing in the Color module with a duo-band dataset, you are essentially balancing the two emission bands, bringing out their prevalence entirely linearly (and thus scientifically useful) as you see fit.

Hope this helps & let us know how you go!
Ivo Jager
StarTools creator and astronomy enthusiast
Burly
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Re: ASI color balance

Post by Burly »

Ivo out of interest just for fun processing in this link https://youtu.be/QV6ObLVRvNk there is a link to the data in the header would the processing in Startools be as you described in the thread above ?

Dave
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Re: ASI color balance

Post by admin »

Burly wrote: Wed Jun 02, 2021 5:53 am Ivo out of interest just for fun processing in this link https://youtu.be/QV6ObLVRvNk there is a link to the data in the header would the processing in Startools be as you described in the thread above ?

Dave
Hi Dave,

That dataset looks about right.
Indeed you would import it exactly as described.

So, for example;
  • Import your dataset via the Compose module, loading the dataset three times; once for red, once for green, once for blue.
    Set "Luminance, Color" to "L + Synthetic L From R(2xG)B, R(GB)(GB) (Bi-Color from OSC/DSLR)".
  • AutoDev to see what we got
  • Crop away stacking artifacts
  • Bin (dataset is a little oversampled)
  • Run Wipe - you can use the defaults or the NarrowBand preset (which assumes no gradients)
  • AutoDev for final stretch
Then, launching Color module should immediately come up with a classic cyan/red bi-color like this;
StarTools_626.jpg
StarTools_626.jpg (271.43 KiB) Viewed 180 times
Sidenote, what is shown in the video is a bit of a no-no; the individual channels are being non-linearly stretched separately, which will cause color artifacts, in turn suggesting emission concentrations (via color) that are not real or comparable with other parts of the image. For the same reason, people don't generally non-linearly stretch channels individually for terrestrial images either (unless for artistic and 90s-album-covers purposes of course :D). Some may consider it pretty, but it is not describing reality as detected/documented. What is allowable, however, is throttling the two bands linearly (as described earlier via the red/green/blue bias sliders).
Ivo Jager
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Re: ASI color balance

Post by Burly »

:thumbsup: Thanks Ivo I will have a play , maybe try 1.8 for comparison once released .

Dave
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Re: ASI color balance

Post by admin »

Burly wrote: Wed Jun 02, 2021 12:26 pm :thumbsup: Thanks Ivo I will have a play , maybe try 1.8 for comparison once released .

Dave
Let us know how you go.
FYI, the 1.8 version Narrowband Accent modules would not be of much use here, given we're not dealing with the augmentation of a visual spectrum datatset...
Ivo Jager
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deanST
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Re: ASI color balance

Post by deanST »

Hi Ivo,

I am using a ASI533MC Pro OSC. I started out with an IDAS LPS-D3 which is a multi-bandpass filter:
Image
The filter is recommended for broadband targets, but I wanted to see how it performs with
the crescent nebula, NGC 6888. Again, my goal is to suppress suburban LP. The imaging characteristics are
as follows:
40 darks: -10C, gain 105, offset 10, 60 sec
40 bias: -10C, gain 105, offset 10, 0.000032 sec
40 flats: -10C, gain 105, offset 10, white balance settings at 50/50 = off, 0.1 sec
(LED tracing panel set on top of stretched white T-shirt)
124 lights: -10C, gain 105, offset 10, white balance settings at 50/50 = off, 60 sec

acquired with William Optics GT71 APO + WO PFlatA6iii FR/FF, HEQ5 mount, ZWO OAG + ASI120mm-mini guide cam
IDAS LPS-D3 filter in Altair Astro filter drawer placed between ASI533MC Pro and OAG. KStars/Ekos for tracking/focus/capture.
Guiding was generally below 0.8 RMS with an abort capture set at 1.0 RMS.
Not a great night for capturing data: some periodic high level thin clouds etc. I culled visually the worst and then had
ASTAP do an evaluation to cull more. Dithering done between every light capture.

Siril for calibration/registration/stacking. Flats calibrated with bias frames. Lights calibrated with darks and calibrated flats,
no normalization in final light stacking. Master calibration dark and flat frames are not Bayered. Calibrated lights are debayered
prior to registration and stacking. I do not use any image processing functions, color balancing or gradient removal etc. in Siril.

When I open as "Linear" and AutoDev, I have a bright yellow/orange image. If I use "Linear from OSC ... " it appears in grayscale.
Should I always open my debayered stacked .fit files from Siril with "Linear from OSC ... " ?
Image
Up til now all of my StarTools processing has been with OSC of broadband targets, so nebula processing is a new challenge
especially with the dense star field that surrounds NGC 6888.

Here is my processing log:

Code: Select all

-----------------------------------------------------------
StarTools 1.7.457
Wed Jun  2 13:15:03 2021
-----------------------------------------------------------
File loaded [r_pp_ngc6888_IDAS_stacked_GESDT.fit].
Image size is 3008 x 3008
--- 
Type of Data: Linear, was not Bayered, or was Bayered + white balanced
--- Auto Develop
Parameter [Ignore Fine Detail <] set to [Off]
Parameter [Outside RoI Influence] set to [15 %]
Parameter [RoI X1] set to [0 pixels]
Parameter [RoI Y1] set to [0 pixels]
Parameter [RoI X2] set to [3008 pixels (-0)]
Parameter [RoI Y2] set to [3008 pixels (-0)]
Parameter [Detector Gamma] set to [1.00]
Parameter [Shadow Linearity] set to [50 %]
--- Bin
Parameter [Scale] set to [scale 70.71% / +1.00 bits / +1.00x SNR improvement]
Image size is 2126 x 2126
--- Crop
Parameter [X1] set to [100 pixels]
Parameter [Y1] set to [100 pixels]
Parameter [X2] set to [2026 pixels (-100)]
Parameter [Y2] set to [2026 pixels (-100)]
Image size is 1926 x 1926
--- Wipe
Parameter [Synthetic Dark/Bias] set to [Off]
Parameter [Gradient Edge Behavior] set to [Absorb 50%]
Parameter [Synthetic Flats] set to [Off]
Parameter [Sampling Precision] set to [256 x 256 pixels]
Parameter [Dark Anomaly Filter] set to [1 pixels]
Parameter [Gradient Falloff] set to [0 %]
Parameter [Synth. Bias Edge Area] set to [100 %]
Parameter [Gradient Aggressiveness] set to [75 %]
Redoing stretch of linear data
--- Auto Develop
Parameter [Ignore Fine Detail <] set to [2.1 pixels]
Parameter [Outside RoI Influence] set to [15 %]
Parameter [RoI X1] set to [842 pixels]
Parameter [RoI Y1] set to [857 pixels]
Parameter [RoI X2] set to [1058 pixels (-868)]
Parameter [RoI Y2] set to [1053 pixels (-873)]
Parameter [Detector Gamma] set to [1.00]
Parameter [Shadow Linearity] set to [50 %]
--- Contrast
Parameter [Expose Dark Areas] set to [Yes]
Parameter [Brightness Retention] set to [Off]
Parameter [Precision] set to [256 x 256 pixels]
Parameter [Shadow Detail Size] set to [10 pixels]
Parameter [Locality] set to [50 %]
Parameter [Shadow Dyn Range Alloc] set to [50 %]
--- HDR
Parameter [Small Detail Precision] set to [Max]
Parameter [Channels] set to [Brightness Only]
Parameter [Algorithm] set to [Reveal DSO Core]
Parameter [Dark/Bright Response] set to [Full]
Parameter [Detail Size Range] set to [207 pixels]
Parameter [Strength] set to [1.2]
--- Wavelet Sharpen
Parameter [Structure Size] set to [Large]
Mask used (BASE64 PNG encoded)
--- SNR-aware Wavelet Sharpening
Parameter [Scale 1] set to [100 %]
Parameter [Scale 2] set to [100 %]
Parameter [Scale 3] set to [100 %]
Parameter [Scale 4] set to [100 %]
Parameter [Scale 5] set to [100 %]
Parameter [Mask Fuzz] set to [4 pixels]
Parameter [Amount] set to [300 %]
Parameter [High SNR Size Bias] set to [85 %]
Parameter [Low SNR Size Bias] set to [0 %]
Parameter [Dark/Light Enhance] set to [50% / 50%]
Mask used (BASE64 PNG encoded)
--- Deconvolution
Parameter [Image Type] set to [Deep Space]
Parameter [Secondary PSF] set to [Dynamic Star Sample Small x Primary]
Parameter [Primary PSF] set to [Moffat Beta=4.765 (Trujillo)]
Parameter [Primary Radius] set to [1.5 pixels]
Parameter [Iterations] set to [11]
Parameter [Error Diffusion] set to [18 %]
Parameter [Mask Fuzz] set to [8.0 pixels]
Parameter [Deringing] set to [50 %]
Mask used (BASE64 PNG encoded)
Mask used (BASE64 PNG encoded)
--- Color
Parameter [Bias Slider Mode] set to [Sliders Reduce Color Bias]
Parameter [Style] set to [Scientific (Color Constancy)]
Parameter [LRGB Method Emulation] set to [Straight CIELab Luminance Retention]
Parameter [Matrix] set to [Identity (OFF)]
Parameter [Dark Saturation] set to [2.5]
Parameter [Bright Saturation] set to [Full]
Parameter [Saturation Amount] set to [243 %]
Parameter [Blue Bias Reduce] set to [1.25]
Parameter [Green Bias Reduce] set to [1.03]
Parameter [Red Bias Reduce] set to [1.72]
Parameter [Mask Fuzz] set to [1.0 pixels]
Parameter [Cap Green] set to [100 %]
Parameter [Highlight Repair] set to [Off]
--- Super Structure
Parameter [Detail Preservation] set to [Linear Brightness Mask]
Parameter [Compositing Algorithm] set to [Multiply, Gamma Correct]
Parameter [Brightness, Color] set to [Only Brightness]
Parameter [Brightness Retention] set to [Off]
Parameter [Mask Fuzz] set to [1.0 pixels]
Parameter [Airy Disk Radius] set to [50 %]
Parameter [Gamma] set to [0.50]
Parameter [Detail Preservation Radius] set to [20.0 pixels]
Parameter [Saturation] set to [100 %]
Parameter [Strength] set to [100 %]
--- Unified De-Noise
Parameter [Grain Size] set to [3.5 pixels]
Parameter [Walking Noise Size] set to [1.0 pixels]
Parameter [Walking Noise Angle] set to [0]
--- Unified De-Noise
Parameter [Scale 1] set to [95 %]
Parameter [Scale 2] set to [95 %]
Parameter [Scale 3] set to [95 %]
Parameter [Scale 4] set to [95 %]
Parameter [Scale 5] set to [50 %]
Parameter [Grain Equalization] set to [0 %]
Parameter [Scale Correlation] set to [23 %]
Parameter [Color Detail Loss] set to [50 %]
Parameter [Brightness Detail Loss] set to [50 %]
Parameter [Grain Dispersion] set to [3.5 pixels]
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Re: ASI color balance

Post by admin »

deanST wrote: Wed Jun 02, 2021 6:32 pm When I open as "Linear" and AutoDev, I have a bright yellow/orange image. If I use "Linear from OSC ... " it appears in grayscale.
Should I always open my debayered stacked .fit files from Siril with "Linear from OSC ... " ?
Ideally you would indeed open the dataset with the "Linear from OSC / not whitebalanced" option. Reason being StarTools can then properly attribute a stronger weighting to your green channel (2 pixels per 4 pixel Bayer matrix patch, vs 1 pixel per 4 pixel Bayer matrix patch for red and blue). This can only happen obviously if nothing else has meddled with that individual channel levels yet.

The orange sounds a little sus though (particularly if a filter was applied). It is typically more in line with a dataset that has already had some sort of color balancing applied.

Would you be able to upload the final stack somewhere, as well as one of the light frames?
Ivo Jager
StarTools creator and astronomy enthusiast
deanST
Posts: 6
Joined: Wed Mar 10, 2021 6:35 pm

Re: ASI color balance

Post by deanST »

Hi Ivo,

link to google drive zip of stack (generalized extreme studentized deviate test)
https://drive.google.com/file/d/1MGp7ot ... sp=sharing

and link to single light
https://drive.google.com/file/d/126hdGz ... sp=sharing

I didn't redo my calibration bias and darks with the color balance factors set to "off" as it seemed unnecessary
since there is no light signal to balance, only the flats and lights.

Here is the stacked flat (windsorized sigma stacking, multiplicative normalization):
https://drive.google.com/file/d/1PvR-rQ ... sp=sharing
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